arXiv subjects

Debottam Das

Publications and source records attributed to Debottam Das.

At least 19 recordsLinked to original sources

arXiv2026

Radiative Corrections to the Direct Detection of Inelastic Scattering of Higgsino-like Neutralino Dark Matter

The direct detection (DD) of Higgsino-like dark matter (DM) through inelastic scattering processes may provide a promising avenue, along with the elastic scattering, when the mass splitting between the neutral Higgsino pairs is extremely tiny. The mass splitting can be reduced further by adopting the on-shell renormalization for the neutral and charged Higgsinos in the MSSM. Moreover, all the one-loop electroweak (EW) corrections to the three-point vertices for the neutralino(s)-Higgs interactions have been considered, while both elastic and inelastic DM-nucleon scattering cross-sections have been calculated primarily through Higgs exchange. Subsequently, the expected number of scattering events in the latest LUX-ZEPLIN (LZ) DD experiment are also computed. Our results highlight a few scenarios in which the inelastic component may exceed the corresponding elastic component, leading to enhanced direct detection scattering rates.

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arXiv2026

Sub-TeV Singlino Dark Matter in light from Sagittarius A$^\ast$ and LUX-ZEPLIN Nuclear-Recoil Event

We investigate the impact of a dark matter density spike surrounding the Milky Way's supermassive black hole (SMBH) on the detectability of Singlino-dominated neutralino dark matter within the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Similar density enhancements, or mini-spikes, around stellar-mass black holes (sBHs), have also been considered. Such a dark matter (DM) candidate typically produces weak indirect detection signals in conventional dark matter halos. Additionally, a Singlino-like lightest supersymmetric particle (LSP) is very difficult to probe at the LHC or through the direct DM search experiments. On top of that, recent observation of the LUX-ZEPLIN 248 keV Nuclear-Recoil Event may hint towards a DM that can be accommodated by a Singlino with mass more than 200 GeV. Keeping these in consideration, we examine the prospects for detecting these sub-TeV dark matter scenarios through gamma-ray observations of the regions surrounding the SMBH Sgr A$^\ast$ and the sBH in the low-mass X-ray binary XTE J1118+480.

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arXiv2026

Unveiling the Vanishing Higgsino-Nucleon Scattering in the MSSM at Next-to-Leading Order

Higgsino dark matter (DM) is considered one of the most well-motivated and minimal DM scenarios arising from supersymmetric extensions of the Standard Model. Motivated by the requirement of electroweak naturalness, Higgsinos are expected to be relatively light, with masses close to the weak scale. While a pure Higgsino state typically evades current direct detection limits, next-to-leading (NLO) order radiative corrections may bring it within the sensitivity of upcoming experiments. On the contrary, a more important consequence, observed specifically near the kinematic threshold for the production of two particles, is that the NLO corrections lower the DM-nucleon cross section below the neutrino floor. We explicitly examine the cancellation mechanism responsible for suppressed Higgsino-nucleon scattering and identify regions of MSSM parameter space where spin-independent cross-sections may vanish.

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arXiv2026

SN1987A Constraints of Light $\boldsymbol{Z'}$ with Non-Mixing Polarisations

The observation of supernova 1987A (SN1987A) provides a unique opportunity to explore new physics beyond the Standard Model (BSM). The production of new particles in the supernova core could accelerate the cooling process, leading to additional energy loss and consequently reducing the duration of the observed neutrino burst at detectors. Therefore, any BSM interactions that affect supernova cooling are subject to stringent constraints from SN1987A observations. In this paper, we revisit the constraints on light gauge bosons (LGBs) by reassessing the validity of underlying assumptions about the polarisation intermixing. We argue that the intermixing between different polarisation modes is suppressed in the low coupling regime. Using the light gauge boson in the $L_\mu-L_\tau$ model as an example, we find that considering the independent energy transport of longitudinal and transverse polarisations can lead to significant modifications of the SN1987A bounds on the parameter space.

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arXiv2025

Constraining lepton flavor violating SMEFT $2q2\ell$ operators from low-energy cLFV processes

Charged lepton flavour-violating (cLFV) processes, which are definite proof of new physics beyond the Standard Model, have remained elusive experimentally till now. Effective Field Theory (EFT) has been very useful in providing information about such new physics through the higher-dimensional operators. These operators respect SM gauge invariance, and they are suppressed by appropriate powers of the energy scale $\Lambda$. In regard to lepton flavour violating (LFV) processes, the Standard Model Effective Field Theory (SMEFT) is shown to be a useful tool for estimating any new physics effect at the scale $\Lambda$. It is worth noticing that a large class of cLFV processes involve both quarks and leptons and thus low-energy observables play a significant role in providing bounds on lepton-flavour-violating 2-quark-2-lepton ($2q2\ell$) operators. Therefore, in this work, we have collected several low-energy cLFV processes that can be addressed within the SMEFT framework and also collected the set of operators responsible for such processes. Keeping in mind the correlation that exists among the SMEFT operators, we want to extract the strongest constraints on these $2q2\ell$ operators.

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arXiv2024

Next-to-leading order QCD corrections to $Z\to q\bar{q}\gamma$, $q\bar{q}\gamma\gamma$

We consider the rare decay channels of the $Z$ boson: $Z \to \text{two}\ \textrm{jets} + \gamma$ and $Z \to \text{two}\ \textrm{jets} +2\, \gamma$. To obtain the widths and distributions for these processes, we compute the effect of NLO QCD corrections to the processes $Z \to q {\bar q}+ \gamma$ and $Z \to q {\bar q} +2\, \gamma$. We find that these corrections reduce the widths of these processes by about $6.03\%$ and $12.39\%$, respectively. The reduction in the partial widths is larger at the jet level. These NLO-improved decay observables may be tested in future runs of the LHC or at future $e^{+}e^{-}$ colliders.

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arXiv2024

Radiative corrections to the direct detection of the Higgsino-(and Wino-)like neutralino dark matter: Spin-dependent interactions

The lightest neutralino ($\tilde{\chi}_1^0$) is a promising dark matter (DM) candidate in the R-parity conserving minimal supersymmetric standard model (MSSM). In this work, we focus on dominantly Higgsino-like and Wino-like $\tilde{\chi}_1^0$ DM, with small admixtures of gauginos and Higgsinos, respectively. In particular, we explore large one-loop corrections to the $\tilde{\chi}_1^0 \tilde{\chi}_1^0Z$ vertex, which can significantly affect the estimation of the spin-dependent $\tilde{\chi}_1^0$-nucleon scattering cross-section in the regions where such DM candidates are viable. We have used the on-shell renormalization scheme to estimate the relevant counterterm contributions. In the parameter region where $\tilde{\chi}_1^0$ is dominantly Higgsino-like, the radiative corrections (including the contributions from the respective counterterms) are substantial and can enhance the $\tilde{\chi}_1^0\tilde{\chi}_1^0Z$ vertex by up to $\sim 120\%$ for the benchmark scenarios we have considered. Further, for an almost pure Wino-like $\tilde{\chi}_1^0$, the increment in the $\tilde{\chi}_1^0\tilde{\chi}_1^0Z$ vertex is up to $15\%$. The corresponding cross-sections with the proton and the neutron can be changed by up to about $50\%$. In addition, including the electroweak box diagrams, the cross-sections can be significantly enhanced, in particular, for the Wino-like $\tilde{\chi}_1^0$.

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arXiv2024

Electroweak renormalization of neutralino-Higgs interactions at one-loop and its impacts on spin-independent direct detection of Wino-like dark matter

A Wino-like neutralino dark matter (DM) in the form of the lightest supersymmetric particle (LSP) has been considered one of the popular paradigms that can naturally accommodate {\it new physics} at a relatively higher scale, typically beyond the reach of the LHC. The constraint on the DM relic density typically implies a lightest neutralino mass $\simeq 2$ TeV. Its observational signature through nuclear recoil experiments, specifically involving DM-nucleon spin-independent (SI) scattering, is not impressive, following its high masses and tiny Higgsino fractions. The theoretical calculations can be improved when we compute all the one-loop electroweak (EW) corrections to the three-point vertices for the neutralino (Wino)-Higgs interactions, which in turn boosts the DM-nucleon scattering cross-sections through the SM-like Higgs exchange. Importantly, we include the counterterm contributions. In addition, we incorporate the other next-to-leading order (NLO) EW DM-quark and DM-gluon interactions present in the literature to calculate the DM-nucleon cross-sections. With the improved and precise theoretical estimates, DM-nucleon scattering cross-sections may increase or decrease significantly by more than $100\%$ compared to leading order (LO) cross-sections in different parts of the parameter space.

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arXiv2024

Implications of Sgr A$^\ast$ on the $\gamma$-rays searches of Bino Dark Matter with $(g-2)_\mu$

We analyse the impact of dark matter density spike around the Milky Way's supermassive black hole (SMBH), Sgr A$^*$, in probing the Bino-dominated neutralino dark matter (DM) $\tilde \chi_1^0$ within the MSSM, which typically produces relatively faint signals in the conventional DM halos. In particular, we explore the indirect search prospects of sub-TeV Bino-Higgsino and Bino-Wino-Higgsino DM in the MSSM, consistent with the supersymmetric predictions required to explain the anomalous magnetic moment of the muon. Typical over-abundance of Bino DM is ameliorated with slepton and/or Wino coannihilations. The lightest neutralino, thus, may be associated with a compressed supersymmetric particle spectrum, which, in general, is difficult to probe at conventional LHC searches. Similarly, for a rather tiny Higgsino mixing, $\tilde \chi_1^0$ does not offer much prospect to assess its predictions at dark matter direct detection searches. Accommodating the inclusive effects of density spike, here, we present the requisite boost factor to facilitate $\gamma-$ray searches of Bino-dominated DM in the MSSM, especially focusing on the Fermi-LAT and HESS observations.

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arXiv2023

Confronting electroweak MSSM through one-loop renormalized neutralino-Higgs interactions for dark matter direct detection and muon $(g-2)$

We compute the next-to-leading order (NLO) corrections to the vertices where a pair of the lightest neutralino couples to CP-even (light or heavy) Higgs scalars. In particular, the lightest neutralino is assumed to be a dominantly Bino-like mixed state, composed of Bino and Higgsino or Bino, Wino, and Higgsino. After computing all the three-point functions in the electroweak MSSM, we detail the contributions from the counterterms that arise in renormalizing these vertices in one-loop order. The amendment of the renormalized vertices impacts the spin-independent direct detection cross-sections of the scattering of nucleons with dark matter. We perform a comprehensive numerical scan over the parameter space where all the points satisfy the present B-physics constraints and accommodate the muon's anomalous magnetic moment. Finally, we exemplify a few benchmark points, which indulge the present searches of supersymmetric particles. After including the renormalized one-loop vertices, the spin-independent DM-nucleon cross-sections may be enhanced up to $20\%$ compared to its tree-level results. Finally, with the NLO cross-section, we use the recent LUX-ZEPLIN (LZ) results on the neutralino-nucleon scattering to display the relative rise in the lowest allowed band of the Higgsino mass parameter in the $M_1-\mu$ plane of the electroweak MSSM.

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arXiv2023

Radiative Corrections to Aid the Direct Detection of the Higgsino-like Neutralino Dark Matter: Spin-Independent Interactions

The lightest neutralino ($\tilde{\chi}_1^0$) is a good Dark Matter (DM) candidate in the R-parity conserving Minimal Supersymmetric Standard Model (MSSM). In this work, we consider the light higgsino-like neutralino as the Lightest Stable Particle (LSP), thanks to rather small higgsino mass parameter $\mu$. We then estimate the prominent radiative corrections to the neutralino-neutralino-Higgs boson vertices. We show that for higgsino-like $\tilde{\chi}_1^0$, these corrections can significantly influence the spin-independent direct detection cross-section, even contributing close to 100\% in certain regions of the parameter space. These corrections, therefore, play an important role in deducing constraints on the mass of the higgsino-like lightest neutralino DM, and thus the $\mu$ parameter.

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arXiv2023

Testing $Z$ boson rare decays $Z\to H_1 \gamma, A_1 \gamma$ with $(g-2)_\mu$, $M_W$, and $BR(h_{\rm SM}\to Z\gamma)$ in the NMSSM

We study the rare decay process of $Z$ boson into photon, accompanied by a CP-even or CP-odd scalar. We present the analytical delineation of the processes through the model-independent parametrizations of the new physics couplings and, finally, consider the Next-to-Minimal Supersymmetric Standard Model to mark out the parameter space where the branching fraction can have the maximum value. As a part of the necessary phenomenological and experimental cross-checks, we aim to fit the anomalous magnetic moment of the muon and $W$ boson mass anomaly through the supersymmetric contributions. We also find that the decays $Z\to H_1 \gamma, A_1 \gamma$ can serve as an excellent complementary test to $BR(h_{\rm SM}\to Z\gamma)$. In fact, to facilitate future searches, we unveil a few benchmark points that additionally satisfy the deviation of $BR(h_{\rm SM}\to Z\gamma)$ from the SM value based on the recent measurements of ATLAS and CMS. Future proposals such as ILC, CEPC, and FCC-ee are anticipated to operate for multiple years, focusing on center-of-mass energy near the $Z$ pole. Consequently, these projects will be capable of conducting experiments at the Giga-$Z$ ($10^{9}$ of $Z$ bosons) and Tera-$Z$ ($10^{12}$ of $Z$ bosons) phases, which may probe the aforesaid rare decay processes, thus the model as well. These unconventional yet complementary searches offer different routes to explore the supersymmetric models with extended Higgs sectors like NMSSM.

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arXiv2022

Production of Singlet dominated scalar(s) at the LHC

The leading order production of an SM singlet-like scalar has primarily been realized through the gluon fusion process by mixing with the $SU(2)_L$ scalar doublet of the model. The dominant part of the physical state, i.e., the singlet component, does not have any role in its direct production. Focusing on such a state with a mass smaller than the SM-like Higgs scalar, we calculate the dominant next-to-leading (NLO) order corrections to its production cross-section. With these improved cross-sections, the present and future LHC limits may become somewhat more stringent.

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arXiv2022

Leptoquark-assisted Singlet-mediated Di-Higgs Production at the LHC

At the LHC, the gluon-initiated processes are considered to be the primary source of di-Higgs production. However, in the presence of a new resonance, the light-quark initiated processes can also contribute significantly. In this paper, we look at the di-Higgs production mediated by a new singlet scalar. The singlet is produced in both quark-antiquark and gluon fusion processes through loops involving a scalar leptoquark and right-handed neutrinos. With benchmark parameters inspired from the recent resonant di-Higgs searches by the ATLAS collaboration, we examine the prospects of such a resonance in the TeV-range at the High-Luminosity LHC (HL-LHC) in the $b\bar{b} \tau^{+}\tau^{-}$ mode with a multivariate analysis. We obtain the $5\sigma$ and $2\sigma$ contours and find that a significant part of the parameter space is within the reach of the HL-LHC.

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arXiv2021

Magnetic Moments of Leptons, Charged Lepton Flavor Violations and Dark Matter Phenomenology of a Minimal Radiative Dirac Neutrino Mass Model

In a simple extension of the standard model (SM), a pair of vector like lepton doublets ($L_1$ and $L_2$) and a $SU(2)_L$ scalar doublet ($\eta$) have been introduced to help in accommodating the discrepancy in determination of the anomalous magnetic moments of the light leptons, namely, $e$ and $\mu$. Moreover, to make our scenario friendly to a Dirac like neutrino and also for a consistent dark matter phenomenology, we specifically add a singlet scalar ($S$) and a singlet fermion ($\psi$) in the set-up. However, the singlet states also induce a meaningful contribution in other charged lepton processes. A discrete symmetry $\mathcal {Z}_2 \times \mathcal {Z}_2^\prime$ has been imposed under which all the SM particles are even while the new particles may be assumed to have odd charges. In a bottom-up approach, with a minimal particle content, we systematically explore the available parameter space in terms of couplings and masses of the new particles. Here a number of observables associated with the SM leptons have been considered, e.g., masses and mixings of neutrinos, $(g-2)$ anomalies of $e$, $\mu$, charged lepton flavor violating (cLFV) observables and the dark matter (DM) phenomenology of a singlet-doublet dark matter. Neutrinos, promoted as the Dirac type states, acquire mass at one loop level after the discrete $\mathcal{Z}_2^\prime$ symmetry gets softly broken, while the unbroken $\mathcal{Z}_2$ keeps the dark matter stable. The mixing between the singlet $\psi$ and the doublet vector lepton can be constrained to satisfy the electroweak precision observables and the spin independent (SI) direct detection (DD) cross section of the dark matter. In this analysis, potentially important LHC bounds have also been discussed.

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arXiv2020

Cancellation in Dark Matter-Nucleon Interactions: the Role of Non-Standard-Model-like Yukawa Couplings

Extensive searches to probe the particle nature of dark matter (DM) have been going on for some decades now but, so far, no conclusive evidence has been found. Among various options, the Weakly Interacting Massive Particles (WIMP) remains one of the prime possibilities as candidates for DM near the TeV scale. Taking a phenomenological view, such null results may be explained for a generic WIMP in a Higgs-portal scenario if we allow the light-quark Yukawa couplings to assume non-Standard Model (non-SM)-like values. This follows from a cancellation among different terms in the DM-nucleon scattering which can, in turn, lead to a vanishingly small direct-detection cross section. It might also lead to isospin violation in the DM-nucleon scattering. Such non-SM values of light-quark Yukawa couplings may be probed in the high luminosity run of the LHC.

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arXiv2020

Enhancing Scalar Productions with Leptoquarks at the LHC

The Standard Model (SM), when extended with a leptoquark (LQ) and right-handed neutrinos, can have interesting new implications for Higgs physics. We show that sterile neutrinos can induce a boost to the down-type quark Yukawa interactions through a diagonal coupling associated with the quarks and a scalar LQ of electromagnetic charge $1/3$. The relative change is moderately larger in the case of the first two generations of quarks, as they have vanishingly small Yukawa couplings in the SM. The enhancement in the couplings would also lead to a non-negligible contribution from the quark fusion process to the production of the 125 GeV Higgs scalar in the SM, though the gluon fusion always dominates. However, this may not be true for a general scalar. As an example, we consider a scenario with a SM-gauge-singlet scalar $\phi$ where an $\mathcal O(1)$ coupling between $\phi$ and the LQ is allowed. The $\phi q \bar{q}$ Yukawa couplings can be generated radiatively only through a loop of LQ and sterile neutrinos. Here, the quark fusion process can have a significant cross section, especially for a light $\phi$. It can even supersede the normally dominant gluon fusion process for a moderate to large value of the LQ mass. This model can be tested/constrained at the high luminosity run of the LHC through a potentially large branching fraction of the scalar to two jets.

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arXiv2019

A Minimal Model of Torsion Mediated Dark Matter

We present a minimal model of fermionic dark matter (DM), where a singlet Dirac fermion can interact with the Standard Model (SM) particles via the torsion field of gravitational origin. In general, torsion can be realized as an antisymmetric part of the affine connection associated with the spacetime diffeomorphism symmetry and thus can be thought of as a massive axial vector field. Because of its gravitational origin, the torsion field couples to all the fermion fields including the DM with equal strength, which makes the model quite predictive. The DM is naturally stable without any imposition of ad-hoc symmetry {\it e.g.,} $\mathcal{Z}_2$. Apart from producing the correct thermal abundance, singlet fermion can easily evade the stringent bounds on the spin-independent DM-nucleon direct detection cross-section due to its axial nature. However, in the allowed parameter space, strong bounds can be placed on the torsion mass and its couplings to fermions from the recent LHC searches. Assuming a non universal torsion-DM and torsion-SM coupling, smaller values of torsion masses may become allowed. In both cases we also study the reach of spin-dependent direct detection searches of the DM.

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